Specialized groups of ribosomes are transferred from follicle cells to oocytes during oocyte development in the ovary. Attempts are being made to isolate these structures by subcellular fractionation, isopycnotic and velocity gradient ultracentrifugation. Their associated proteins are being purified. The preparation can then be used for the study of translation mechanisms. We have demonstrated the secretion of nucleoside triphosphate hydrolases by secretory cells of the oviduct. These enzymes then bind to the isolate and characterize these enzymic complexes and to assess their roles in fertilization and early blastocyst formation.